This article is about own group favoring behaviour and cognition in a strategic sense. For other phenomena rated to psychological group formation, see Ingroups and outgroups.

Ingroup bias, sometimes known as in-group favoritism, in-group–out-group bias or intergroup bias, refers to a pattern of favoring members of one’s in-group over out-group members. This can be expressed in evaluation of others, allocation of resources and many other ways.[1]

Experiments in psychology have shown that people will award others higher payoffs even when the "group" they share seems random and arbitrary, such as having the same birthday, having the same final digit in their US Social Security Number, or even being assigned to the same flip of a coin.

The interaction has been researched by many psychologists and linked to many theories related to group conflict and prejudice. The phenomenon is primarily viewed from a social psychology standpoint rather than a personality psychology perspective. Two prominent theoretical approaches to the phenomenon of ingroup favoritism are realistic conflict theory and social identity theory. Realistic conflict theory proposes that intergroup competition, and sometimes intergroup conflict, arises when two groups have opposing claims to scarce resources. In contrast, social identity theory posits a psychological drive for positively distinctsocial identities as the general root cause of in-group favouring behavior.

Ingroup effects appear to be stronger, however, when the group is smaller relative to another high-power group.

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In 1906, the sociologist William Sumner posited that humans are a species that join together in groups by their very nature. However, he also maintained that, beyond this, humans had an innate tendency to favor their own group over others; saying, "Each group nourishes its own pride and vanity, boasts itself superior, exists in its own divinities, and looks with contempt on outsiders" (p. 13).[2] This is seen on the group level with ingroup-outgroup bias, and when experienced in such larger groups as tribes, ethnic groups, or nations, it is referred to as ethnocentrism.

Competition between groups for resources has been suggested as the cause of negative prejudices and stereotypes of the out-group, a phenomenon called realistic conflict theory, or realistic group conflict.[3] The Robbers Cave Experiment is commonly used to exemplify this perspective. In this experiment, 22 eleven year-old boys with similar backgrounds were studied in a mock summer camp situation. The boys were broken into two groups of twelve and were studied on their in-group out-group behavior in several different situations. The research revealed evidence that regardless of two groups’ similarity, group members will behave viciously toward the out-group when competing for limited resources.[4] The in-group/out-group bias could readily be seen in the boys' behaviors toward each other. They underestimated the performance of the other group and overestimated the performance of their own group. Moreover, "the pro-ingroup tendency went hand in hand with the anti-outgroup tendency".[5]

It is argued that one of the key determinants of group biases is the need to improve self-esteem. That is individuals will find a reason, no matter how insignificant, to prove to themselves why their group is superior. This phenomenon was pioneered and studied most extensively by Henri Tajfel, a British social psychologist who looked at the psychological root of in-group/out-group bias. To study this in the lab, Tajfel and colleagues created what are now known as minimal groups (see minimal group paradigm) which occur when “complete strangers are formed into groups using the most trivial criteria imaginable”. In Tajfel’s studies, participants were split into groups by flipping a coin, and each group then was told to appreciate a certain style of painting none of the participants were familiar with when the experiment began. What Tajfel and his colleagues discovered was regardless of the fact that a) participants did not know each other, b) their groups were completely meaningless and c) none of the participants had any inclination as to which “style” they like better, almost always across the board participants “liked the members of their own group better and they rated the members of their in-group as more likely to have pleasant personalities”. By having a more positive impression of individuals in the in-group, individuals are able to boost their own self-esteem as members of that group.[1]

Robert Cialdini and his research team looked at the number of university T-shirts being worn on college campuses following either a win or loss at the football game. Not surprisingly, the Monday after a win there were more T-shirts being worn, on average, than following a loss.[1][6]

In another set of studies done in the 1980s by Jennifer Crocker and colleagues, self-esteem was studied using minimal group processes in which it was shown that individuals with high self-esteem who suffer a threat to the self-concept exhibit greater ingroup biases than people with low self-esteem who suffer a threat to the self-concept.[7] While some studies have supported this notion of a negative correlation between self-esteem and in-group bias,[8] other researchers have found that individuals with low self-esteem have a higher prejudice to both in-group and out-group members.[7] Some studies have even showed that high-self-esteem groups showed a greater prejudice than did lower self-esteem groups.[9] This research may suggest that there is an alternative explanation and additional reasoning as to the relationship between self-esteem and in-group/out-group biases. Alternatively, it is possible that researchers have used the wrong sort of self-esteem measures to test the link between self-esteem and in-group bias (global personal self-esteem rather than specific social self-esteem).[10]

Social psychologists have long made the distinction between ingroup favouritism and outgroup negativity, where outgroup negativity is the act of punishing or placing burdens upon the outgroup.[11] Indeed, a significant body of research exists that attempts to identify the relationship between ingroup favouritism and outgroup negativity, as well as conditions that will lead to outgroup negativity.[12][13][14] For example, Struch and Schwartz found support for the predictions of belief congruence theory.[15] The belief congruence theory concerns itself with the degree of similarity in beliefs, attitudes, and values perceived to exist between individuals. This theory also states that dissimilarity increases negative orientations towards others. When applied to racial discrimination, the belief congruence theory explains that it’s the perceived dissimilarity of beliefs that has more of an impact on racial discrimination than race itself.